1. Field of the Invention
Radiation sensitive compounds which polymerize rapidly are useful to form decorative or protective film coatings for a wide variety of substrates. Of particular interest are radiation curable compounds that impart good slip properties to compositions for forming protective films of high gloss for paper and paperboard substrates.
2. Description of the Prior Art
Silicon-containing compounds useful as slip-aid and flow-control agents in coating compositions are well known. For example, British Pat. No. 927,517 to Farbe Werke Hoechst A.G. discloses polydimethylsiloxanes as flow-control agents for paints and German Pat. No. 1,092,858 to Farbenfabricken Bayer discloses phenyl-substituted polysiloxanes as flow improvement agents for coating compositions. Typically, these conventional silicon-type lubricating agents are somewhat incompatible with other components of the coating compositions so that foaming can result when the compositions are applied to a substrate, especially where the silicone agent is present in amounts greater than about 2 percent by weight of the composition. The cured film thus may be pitted and have uneven gloss. Reduction in film integrity can also result because the silicone slip agents do not cure in the conventional sense inasmuch as there is usually no cross-linkable moiety present in the silicone compound. More often, the slip-aid agents are merely occluded in the film, typically at the surface layer. When the surface layer wears away, the film can lose to a substantial degree its slip characteristics.
Radiation sensitive coating compositions requiring good film slip properties are those typically used for forming protective films on paper and paperboard substrates, such as magazine covers and record jackets, which articles having cured films thereon must slide easily when stacked or unstacked by paper handling machinery. Also, compositions for this application must cure quickly and form abrasion resistant films. Moreover, the films must exhibit fairly high gloss. Conventional radiation curable compositions for use in the paper coating industry do not provide films having the combination of good slip, fast cure and abrasion resistance.